TABLE 2.
Independent Risk Factors for Intensive Care Unit–Acquired Extended-Spectrum β-Lactamase (ESBL)–Producing Klebsiella Species or Escherichia coli
| Study variable | Adjusted odds ratio (95% confidence interval) | P |
|---|---|---|
| ESBL-positive prior room occupanta | 1.39 (0.94–2.08) | .10 |
| Colonization pressure (>7%)b | 2.17 (1.59–2.96) | <.01 |
| Renal disease | 1.68 (1.20–2.35) | <.01 |
| Anti-MRSA therapyc | 1.72 (1.25–2.37) | <.01 |
| Antipseudomonal β-lactam therapyc | 2.17 (1.43–3.30) | <.01 |
note. ESBL, extended-spectrum β-lactamase; ICU, intensive care unit; MRSA, methicillin-resistant Staphylococcus aureus; OR, odds ratio; CI, confidence interval.
Crude odds ratio (95% confidence interval) was 1.88 (1.29–2.74), with P < .01.
These variables were dichotomized at the median, because variables were not normally distributed.
Antimicrobial drug exposure was defined as antibiotic therapy ordered during the period between ICU admission and ICU discharge for patients who did not acquire an ESBL-producing pathogen and between ICU admission and the date on which a positive culture specimen was collected for patients who acquired an ESBL-producing pathogen. Colonization pressure was defined as the daily proportion of patients positive for ESBL-producing pathogens. For each patient, colonization pressure was calculated as the average of the daily proportion of patients positive for an ESBL-producing pathogen during their time at risk. A median colonization of 7% indicates that, in 50% of the patient population, colonization pressure was less than 7%.